Process for the treatment of clay and kaolin by elutriation.



' BOTHO SCHWERIN, 0F FRANKFORT-0N-THE-MAIH, GERMANY, ASSIGNOR I'D ELEKTRO OSMOSE AKTIENGESELLSCHAFT (GRAE SCHWERIN GESELLSCHAET), 0F FRANK- FORT--ONTHE-MAIN, A CORPORATION.

PROGESFd FOR THE TREATMENT 6F CLAY No Drawing.

To all whom it may concern:

Be it known that I, Borne ,Scnwnnm,

a subject of the German Emperor, residingat Frankfort-onthe-Main, Germany, have invented certain new and useful improvements in Processes for the Treatment. of Clay and Kaolin by Elutriation, of which the following is .a a specification.

When clays as they occur in nature, for instance crude kaolin or plastic clay, which are always admixed with particles of various other-minerals, are suspended in water, the clay or kaolin. may be obtained by elutriation in more or less pure condition and more or less satisfactory yield.

. The deposits are, however, of a voluminous characterand still. contain much water. Even after standing for many weeks the deposit from a kaolin suspension, for instance, may still contain about per cont ct water after supernatant water has been drawn .otl'.

o The present invention relates to an improvement in the elutriation process, WllBFB- by the material is obtained in a more solid condition, that is to say more free from Water, the yield of pure material being at the same time considerably increased.

The-invention consists in permitting the 7 material to settle While it is in the sol. condition. All-n'iaterizds which settle in this condition yield solid deposits. This solid form is due to a kind of electrical surface tension which not only expresses the Water from between the several particles, so that a higher degree of dehydration ofthe re spective layers is attained, but also, by the internal contraction of the deposit, expresses the finer suspensoids from between the deposited particles, so that the former are separated from the latter and remain in suspension. These suspended particles also gradually settle and ail'ord further fractions of higher degree of fineness in solid form free from water. in this manner the yield is increased.

The invention will. be further explained by reference to a kaolin suspension. The

crude kaolin contains a considerable pro portion of fine particles of other minerals, hereinafter termed shore, and the particles Specification of Letters Patent.

AND KAOLIN BY EZUIRI ATICN.

Patented July 1?,1911'3.

of kaolin are in partso finely united with the slime. that they cannot be separated mechanically. V hen. such a kaolin suspension is allowed to rest, a portion of the kaolin does indeed settle, but it forms a voluminous, spongy deposit, rich in Water. After settling for I content of the deposited kaolin still amounts to about 60 per cent. Moreover, a large part of the kaolin is lost as it' is carrie'fdto the bottom by the slime which retains it.

If, hormver, the suspended. kaolin is caused to pass into the sol condition, that is, to undergo an increase in its degree of disperslon, by one of the methods usual in colloid chemistry and is allowed to'stand, the aforesaid advantages arise. For the purpose of producing the sol condition there may, for

example, be added to the suspension a small proportion of caustic soda lye or another basic electrolyte. In the case of indifferent substances it is preferable to add ,tothe suspension a suitable colloid body in addition to a. suitable electrolyte. Under these conditions, if the grinding has been sufficient, an increase in the degree of dispersion of both the kaolin and the slime occurs. First the impurities such as sand,

mica and coarse constitutents' settle from' the suspension.

Then the slime loses its collidal condition and settles fraction-ally 1 solid :t'ornn'in high degree free from Wator, This also happens by degrees in the case of the kaolin, which gradually deposits :t'ractionally in a hard in H1.

several weeks, the ater These fractions are compressed by a kind of. electrical surface tension of the particles to a deposit or cake so solid that it contains only about 25-36 per cent. of water. This internal contraction. of the cake of slime causes a firm deposition of the separate par-- ticles on each other without intermediate spaces, whereby the suspension between. the particles is: expressed from the cake so that fine particles of kaolin are expel-led into the water and are subsequently deposited as another fraction. Owing to this phenomenon, the yield of kaolin increases; for the kaolin is now no longer incased and retained by the deposited slime as in the usual elutriation process. In the case of certain kinds of kaolin it is possible to obtain by the present invention an increased yield of 100 per cent. as compared with the usual elutriation.

Example 1lncrcasing the degree of dryabout 10 er cent. of water,'or' freed from water in ter-presses. In the latter case the material removed from the press contains 707 5 per cent. of dry substance. According to the present invention, the kaolin is suspended in water and sodium silicate is added to it.

The following fractions were obtained Bcsl due ki lps haying 9.3. at d y subst mce.

is obtained by filter pressing.

u u u u u n u u u l a; 26 7911 4:14 5 7s Residues 1 and 2 consisted of sand and slime and deposited, as will be apparent, in a much drier form than in the usual technical elutriation process, wherein the slime is completely fluid. Residues 3 and 4 consist of kaolin with 78-79 per cent. of dry substance, which isconsiderably higher than Example 2-] ncreasing the yield-in order to show how by the present process the yield may be increased, the following example is adduced, namely of a washed slime,

an industrial product, from which 39.4 per cent. of kaolin was obtainable whichwould have been lost by the usual process.

2O kilos of the slime were suspended in liters of water and 150 c. c. of sodium silicate'solution (Na siO 1 part, water 2 parts) were added.

'1 hree fractions were obtained, namely Fraction 1: 11.4 kilos=60 per cont.

n 2250 u n Fraction 1 consisted of fine mineral particles (slime), fractions 2 and 3 were pure kaolin, coarse and line respectively, together amounting to 39.4 per cent.

This quantity of kaolin therefore was rendered available by application of the present invention.

WVhat I claim is:

1. A process of separating clay and kaolin from associated materials which comprises suspending in water the mixture to be treated, increasing the degree of dispersion of suspended matter, and allowing such matter to settle, the amount of water and the increase in the degree of dispersion bein so proportioned as to produce a sediment aving not more than about 30 per cent. out water.

2. A process of separating clay and kaolin -from slime which comprises suspending clay and containing slime in water, inreasi-n'g the degree of dispersion of both the slime and kaolin, and then allowing these materials to settle, and so proportioning'; til amount of water and the increase in the d-igrce of dispersion as to effect a fractional sedimentation, and to produce a slime sediment substantially free from kaolin, and a kaolin sediment containing not more than about 30 per cent. of water.

' In testimony whereof I ailix my signature in presence of two witnesses.

BOTH O. SCI-IWERIN. Witnesses:

JEAN GRUND, Gus HICHENTHAL. 

